1. Field of the Invention
The present embodiments relate to an organic thin film transistor and a flat panel display including the same. More particularly, the present embodiments relate to an organic thin film transistor, providing smoother movement of holes between a source electrode or a drain electrode and a p-type organic semiconductor layer, and a flat panel display device including the organic thin film transistor.
2. Description of the Related Art
After the development of polyacetylene, which is a conjugate organic polymer representing semiconductor characteristics, research into a transistor using an organic material is being pursued in various fields, such as, functional electronic devices and optical devices, because of the characteristics of an organic material and because the organic material can be synthesized in various ways and easily formed into a fiber or a film and other advantages of the organic material, which are elasticity, conductivity, and low production costs.
Conventional silicon thin film transistors include a semiconductor layer that has a source region and a drain region each doped with impurities at a high concentration and a channel region formed between the source and drain regions. The conventional silicon thin film transistors further include a gate electrode insulated from the semiconductor layer and facing the channel region and a source electrode and a drain electrode contacting the source and drain regions, respectively.
However, since the conventional silicon thin film transistors having the above-described structure are costly, breakable by sudden impacts from external forces, and are produced at a high temperature, for example, at about 300° C. or higher, the transistors cannot be placed on a plastic substrate or the like.
In particular, flat panel display devices, such as, liquid crystal display device (LCDs) or electroluminescence display devices (ELDs), use a thin film transistor to serve as a switching device and a pixel-driving device. Furthermore, attempts to use a substrate formed not of glass but of plastic have continued to facilitate a recent trend toward large, thin, and flexible flat panel display devices. However, when a plastic substrate is used, conventional silicon thin film transistors should be produced at a low temperature instead of a high temperature. Consequently, alternatives to conventional silicon thin film transistors are needed.
This problem can be solved by using an organic film as a semiconductor layer of a thin film transistor.
However, the organic thin film transistor has a disadvantage in that a contact resistance among a source electrode, a drain electrode, and an organic semiconductor layer is large. In other words, in contrast with the silicon semiconductor layer included in the conventional silicon thin film transistor, the organic semiconductor layer included in the organic thin film transistor cannot be doped with impurities at high concentration. Accordingly, the contact resistance among a source electrode, a drain electrode, and an organic semiconductor layer increases, to the point that an ohmic contact is impossible.